Nutrition & Food Science
Permanent URI for this communityhttp://hdl.handle.net/1903/2267
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Item COMBINED EFFECTS OF SUNLIGHT AND TITANIUM DIOXIDE NANOPARTICLES ON DIETARY ANTIOXIDANTS AND FOOD COLORS(2014) Li, Meng; Lo, Yangming M; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The breakthroughs in material science have enabled industrialized fabrication and production of nanomaterials. To date, nanoscale materials have been shown to exhibit improved functionalities, providing numerous novel applications. Titanium dioxide (TiO2) nanomaterials have been widely utilized in the food industry due to their unique properties under light. Upon light irradiation, TiO2 nanoparticles (NPs) generate highly active reactive oxygen species (ROS) therefore can be potentially used as light tunable antibacterial packaging materials. Moreover, it has also been reported that a considerable amounts of TiO2 NPs is found as an ingredient in food, cosmetics, personal care, and pharmaceutical products. With improved photoactivity, nano TiO2 generates higher amounts of ROS upon light irradiation that can result in oxidative damage. The present study investigates the combined effect of sunlight irradiation and TiO2 nanoparticles (NPs) on sensitive antioxidants and food colors. Upon simulated sunlight irradiation, TiO2 NPs weakened the radical scavenging ability of antioxidants by photocatalytic decomposition or surface adsorption. The decomposition of a widely used food azo dye FD&C Yellow No. 5 (tartrazine) by sunlight activated TiO2 NPs was also investigated. The mechanism is pH dependent, involving the depletion of two main ROS species, hydroxyl radical and singlet oxygen. Compared with the photocatalyst TiO2 sample P25, food-grade TiO2 NPs also showed strong ROS promoting ability and resulted in the degradation of selected synthetic dyes, including tartrazine, allura red and sunset yellow, as well as the semi-synthetic food color chlorophyllin sodium copper salt. Thus, TiO2 NPs should be used with caution when added to or used in contact with food ingredients that depend solely on the existing antioxidants and colors in the system. The ability of TiO2 to generate ROS was found to be phase-dependent. The rutile phase TiO2 generated the least amount of ROS when compared to anatase phase and did not lead to noticeable color degradation in the studied light irradiation period. Thus, when possible, rutile phase TiO2 should be used in food as it provides a more stable system compared to anatase and mixed phases. The results in this study provide clear insights on setting up proper protocols for evaluating and administrating nanosized TiO2 in food uses.Item Promotion of Value-Added Uses of Soybeans(2011) Slavin, Margaret; Yu, Liangli; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soybeans contain a wealth of health-promoting phytochemicals, the amounts of which are known to vary considerably across genotypes and growing conditions. The present work is dedicated to better understand these variations and to improve the methods for investigating soy phytochemicals. To address the first of these concerns, low-linolenic soybeans and colored seed coat soybeans were investigated for their health beneficial components, as well as their chemical and biological properties. A study of low-linolenic soybeans showed their similar antioxidant activity, total phenolics, and isoflavones to normal fatty acid soybeans. The potential for a different trend in tocopherols and lutein was observed between low-linolenic and regular fatty acid soybeans, but the limited study size prevented a definitive conclusion. This work was the basis for further studies on low-linolenic soybeans not included in this report. Subsequently, a study of eighteen soybeans of brown, green, yellow and black seed coat colors concluded that black seed coat soybeans had significantly higher scavenging activity against hydroxyl, peroxyl, and ABTS+ radicals. Black seed coat soybeans also contained higher total phenolic contents and isoflavones than the other colored soybeans, and were the only color to contain the anthocyanin cyanidin-3-glucoside. However, when soybean extracts were tested for their ability to prevent colon cancer cell proliferation, seed coat color and chemical composition were not necessarily predictive of an extracts' bioactivity. Lastly, a new analytical method was developed and validated for quantification of phytosterols, tocopherols and carotenoids, three separate classes of soy lipophilic phytochemicals, in a single extraction and HPLC run. A ternary, isocratic solvent system of acetonitrile, methanol and water (48:22.5:29.5, v/v/v) was used to achieve separation on a phenyl column. Evaporative light scattering detection (ELSD) was used to quantify beta-sitosterol, stigmasterol, campesterol, alpha-, delta- and gamma- tocopherols, while lutein was quantified with visible light absorption at 450 nm. This method offers a more efficient alternative to separate, individual methods for quantifying lutein, tocopherols and sterols in soybeans.